1. Field of the Invention
The present invention relates to a method for molding a bead portion of a green tire capable of easily winding a carcass ply without the necessity of preliminarily forming a bending portion at the carcass cords when forming a green tire of so-called bead-wind structure in which both end portions of a carcass ply are wound around bead cores, and to a bead portion molding device employed for this purpose.
2. Description of the Related Art
As illustrated in FIG. 9, it is recently being suggested to employ a bead-wind structure in heavy-duty tires utilizing a carcass ply (a) of steel cords. In such a bead-wind structure, carcass wound portions (a2), in which the carcass ply is wound by substantially a whole round around the bead cores (b), are formed on both sides of a carcass main portion (a1) that bridges between bead cores (b, b) to thereby fix both end portions of the carcass ply (a).
In such a structure, tip ends (ae) of the carcass wound portions (a2) are interrupted proximate of the periphery of the bead cores (b) so that stress through deformation of the beads hardly acts onto the tip ends (ae). It is accordingly of advantage that damages such as loosening of cords originating from the tip ends (ae) can be effectively restricted. However, in this structure, the entire length of the carcass wound portions (a2) is short and a winding radius thereof small while a flexural rigidity of the carcass cords (steel cords) is large. A drawback is thus exhibited in that it is difficult to easily and accurately wind the carcass ply (a) around the bead cores (b) in the course of manufacturing a green tire.
It has thus been suggested in, for instance, Japanese Patent Application Laid-Open No. 2001-246675 or Japanese Patent Application Laid-Open No. 2001-246676 to preliminarily form a plastic-deformed bending portion in the carcass ply in which carcass cords are partially bent at respective positions that suit corner portions of the bead cores.
However, when bending is performed to the carcass cords, the rigidity and strength of the carcass cords will be degraded due to the partial bending so that there is a danger that damages originating from the bent portions of the cords are induced during running.